This invention relates to a horn type loudspeaker, and more particularly a horn type loudspeaker provided with an equalizer which prevents phase interference occurring at the throat of the horn.
In a loudspeaker of this type, the radiation impedance encountered when transmitting the vibration of a diaphragm to a horn is high because of the provision of the horn, so that this type of loudspeaker can radiate sound at high efficiency. However, such horn has some problems regarding the construction thereof. For example, in a rear type horn loudspeaker disclosed in U.S. Pat. No. 4,050,541 issued on Sept. 27, 1977 to Clifford A. Henricksen, current is passed through a voice coil disposed in an air gap between pole piece elements to vibrate a diaphragm integrated with the coil, the diaphragm being resiliently supported by a frame through a spider, i.e., a suspension member. In this construction, the entire periphery of the diaphragm is connected to the inner edge of the ring shaped spider made of a resilient member.
With the construction disclosed in this U.S. Patent, a portion extending from the diaphragm into the air gap and wound with the coil, the suspension member and the pole piece define an airtight chamber which debases the damping effect of the suspension member which absorbs the vibration created by the axial movement of the diaphragm.
With this construction, the suspension member is required to have the ability of supporting the diaphragm and to damp the vibration. In order to satisfy these two requirements, it is impossible to make too large the axial compliance of the diaphragm. Where the thickness, material and the difference between the inner and outer diameters of the supporting members are selected so as to increase the axial compliance the radial displacement becomes excessive. As a consequence, the coil disposed in the air gap will come into contact with the pole piece and damaged. Furthermore the diaphragm disposed to oppose an equalizer with a small air gap therebetween would contact the equalizer thus damaging the same.
Although these problems can be obviated by increasing the air gap between the pole pieces and the air gap between the diaphragm and the equalizer but widening of these air gaps decreases the sound converting efficiency and the performance of the equalizer.